Field
This disclosure is generally related to distribution of digital content. More specifically, this disclosure is related to providing notification by a content producing device to a content requesting device of a potential timeout event in order to keep an Interest alive in a content centric network (CCN).
Related Art
The proliferation of the Internet and e-commerce continues to create a vast amount of digital content. Content-centric network (CCN) architectures have been designed to facilitate accessing and processing such digital content. A CCN includes entities, or nodes, such as network clients, forwarders (e.g., routers), and content producers, which communicate with each other by sending Interest packets for various content items and receiving Content Object packets in return. CCN Interests and Content Objects are identified by their unique names, which are typically hierarchically structured variable length identifiers (HSVLI). An HSVLI can include contiguous name components ordered from a most general level to a most specific level. As an Interest packet is routed through the network from a content requesting node to a content producing node, each intermediate CCN router adds an entry in its Pending Interest Table (PIT) corresponding to the Interest and forwards the Interest to the next CCN router. When a matching Content Object packet is sent from the content producing node back to the requesting node, it follows the reverse path of the Interest. Each intermediate CCN router forwards the Content Object along the requesting interfaces listed in the corresponding PIT entry and subsequently removes the PIT entry, indicating that the Interest has been fulfilled.
A PIT entry can also be removed by a CCN node (or router) when the PIT entry times out. A node can select any time out value that the node deems appropriate upon adding an Interest to its PIT. PIT entries can time out under different scenarios. One case is due to congestion in the network, which results in the system dropping the Interest or the matching Content Object. Another case is when the content producing node or application responsible for generating the matching Content Object needs to perform a computationally intensive task (e.g., that takes 45 seconds) before it can send a response back. In both cases, PIT entry timeouts can lead to the requesting node re-expressing the Interest, sometimes repeatedly and over a short period of time. PIT entry timeouts can also cause intermediate CCN routers to transmit the re-expressed Interests on multiple interfaces, thus increasing network traffic and creating additional congestion.